Our objectives are to learn more about the biochemical mechanisms involved in the induction of cancer by chemicals by (1) studying mechanisms by which chemicals are metabolized in susceptible tissues; (2) by examining the damage and repair of DNA in susceptible tissue; and (3) by looking at factors involved in the progression of the carcinogenic process. The rat is the main experimental animal being used. Carcinogens employed include 2-acetylaminofluorene and related aromatic amines, N-methyl-N-nitrosourea, and several dialkylnitrosamines. Tissues being studied include liver, mammary gland, and urinary bladder.